C(n + a, a) * C(n + b, b),
where C(m, n) is the binomial cofficient.

> C(n + a, a) * C(n + b, b),
> where C(m, n) is the binomial cofficient.
Thanks Li Yi for providing us with the mathematical model
of several problems, it would help us a lot. I really
appreciate it. Could you drop me an email, my email address
is raynaldo_adp@yahoo.com just in case I need assistance
from you.

Thank you first.
I cannot send mail to you because my mail server returned:

<raynaldo_adp@yahoo.com>: host mx2.mail.yahoo.com
[64.157.4.84] said: 554 delivery error: dd This user
doesn't have a yahoo.com account

You can mail me.
My email is: lee-e.@263.net
(Pay attention that there's a period before `@`)

> Thanks Li Yi for providing us with the mathematical model
> of several problems, it would help us a lot. I really
> appreciate it. Could you drop me an email, my email
address
> is raynaldo_adp@yahoo.com just in case I need assistance
> from you.